1. Field of the Invention
The present invention relates to an image pickup apparatus.
2. Description of the Related Art
In a conventional phase-difference AF (auto focus), a phase-difference signal only in one direction could be acquired from a signal from a set of pixel sets. Whereas, it is said to be desirable to acquire a phase-difference signal in two directions for calculating a highly accurate defocus amount, independent of an object.
In Japanese Patent Application Laid-open Publication No. 2000-9990, a structure in which, an optical system for a phase-difference AF is arranged, and a phase-difference signal in two directions is acquired, has been disclosed. In the conventional phase-difference AF having such structure, two sets of pixel sets are disposed, and a phase-difference signal of a different direction is acquired from each pixel set.
Moreover, in Japanese Patent Application Laid-open Publication Nos. 2000-156823 and 2008-40087, a proposal in which a pixel for ranging which outputs a signal is disposed in an image pickup element for acquiring a signal for image formation, has been made.